Pyrotechnic circuit breaker

ABSTRACT

A circuit breaker including a pyrotechnic element configured to ablate, tear, or cut a portion of the circuit. The portion of the circuit to be broken may be formed to be readily broken and/or may be a current load-based fuse. Also, the circuit breaker may be configured to ensure predictable progressive lateral tearing of the portion of the circuit to be broken; the circuit breaker may optionally be configured so that substantially all of the pyrotechnic element&#39;s output is focused on breaking the circuit; and the circuit breaker may optionally include a positive displacement mechanism that, after actuation of the pyrotechnic igniter, prevents the circuit breaker from inadvertently re-closing.

BACKGROUND OF THE INVENTION

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/688,020 entitled “Pyrotechnic Circuit Breaker,” filed Oct.17, 2003.

The present invention is directed generally to the field of circuitbreakers, and more particularly, to a circuit breaker including apyrotechnic element for breaking the circuit.

The circuit breakers used in various electrical systems in motorvehicles such as automobiles, trucks, buses, fixed wing aircraft,helicopters, marine vessels and the like, have conventionally employedfuse-type resistor elements that burn out when an excessive level ofcurrent passes through the element, causing a break in the circuit.

Various substitutes for such conventional fuses have also been devised,such as to permit breaking of a circuit in response to abnormalconditions (such as the collision of a vehicle) that would notnecessarily create an immediate excessive current load in a fuse. Forexample, U.S. Pat. No. 6,194,988 to Yamaguchi et al. teaches the use ofa sort of “hot plate” that is spring-biased against a relatively lowmelting point fuse section, with the hot plate being heated by anattached igniting device that contains a solid combustion agent; theigniting device is rapidly activated such as in the case of a collision,heating the hot plate which then melts the adjacent fuse section and(due to the spring bias) drives through the molten fuse section, cuttingit out and thereby breaking the circuit. Devices such as that of the'988 patent based on melting that is induced by conducted heat, however,cannot exploit the rapidity of a pyrotechnic ignition because theprocess of heat conduction is quite slow in comparison to the speed of apyrotechnic ignition. Such devices can also be relatively complex andcostly.

There are also a number of recent battery cable clamp breaker devicesthat include a pyrotechnic device (configured to ignite in response toan abnormal condition such as a collision of the vehicle containing thedevice) that physically drives apart two parts of the clamp or terminalso that they are no longer electrically connected, such as in U.S. Pat.No. 5,725,399 to Albiez et al. and U.S. Pat. Nos. 5,818,121, 6,144,111,and 6,171,121 to Krappel et al. This type of device is generally capableof deploying quickly, e.g., in the case of a collision so as to reducethe chance of an electrical fire in the damaged vehicle irrespective ofwhether the conditions would rapidly cause a conventional fuse to blow.Yet such devices are in general a relatively complex, costly, and/orbulky way to provide the function of pyrotechnically-induced circuitbreaking. Moreover, such devices do not intrinsically involve aconventional (i.e., current load-based) fuse, so if it were desired toalso retain the conventional function of current load-based breaking insuch a circuit breaker, a conventional fuse would need to be added as adistinct additional component, thus rendering the resulting device yetmore complicated and costly.

Finally, U.S. Pat. No. 3,991,649 to Patrichi and U.S. Pat. No. 5,877,563to Krappel et al. teach circuit breaker devices in which a pyrotechnicdevice is used to propel a cutter through a wire or to unplug aconnector. Neither patent, however, teaches the pyrotechnically-drivenbreaking of a current load-based fuse in a circuit.

SUMMARY OF THE INVENTION

A circuit breaker according to the present invention includes apyrotechnic igniter and a portion of the circuit that breaks as a resultof the ignition of the pyrotechnic igniter. The portion of the circuitto be broken may also be a current load-based fuse.

In a separate and independent aspect of the invention, the circuitbreaker may be configured to ensure predictable progressive lateraltearing of the portion of the circuit to be broken.

Optionally, the circuit breaker may be configured so that substantiallyall of the pyrotechnic igniter's output is focused on breaking thecircuit. Also optionally, the circuit breaker may include a positivedisplacement mechanism to ensure that the circuit, once broken byactuation of the pyrotechnic igniter, cannot be re-closed inadvertently.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective, partly cut-away view of an embodiment of apyrotechnic circuit breaker according to the present invention,utilizing a cutting projectile.

FIG. 2 is a transverse sectional view of the embodiment of FIG. 1.

FIG. 3 is a lateral sectional view of another embodiment of apyrotechnic circuit breaker according to the present invention, notutilizing a cutting projectile, but a focused ignition output.

FIG. 4 is a lateral sectional view similar to that of FIG. 3, butdepicting an alternative embodiment in which the portion of the circuitto be broken has an enlarged impact area, which may optionally be usedwith a cutting projectile.

FIGS. 5-10 depict another embodiment of a pyrotechnic circuit breakeraccording to the present invention, utilizing a slug that tears aportion of the circuit. FIG. 5 is a perspective view, FIG. 6 is a partlycutaway perspective view, and FIG. 7 is a transverse sectional view, ofthe circuit breaker. FIGS. 8 and 9 are top-down views of the circuitbreaker's lower housing respectively with and without the bolt-on fusestrip, and FIG. 10 is a sectional view of the lower housing through theline A-A shown in FIG. 9.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIGS. 1 to 3, a preferred embodiment of a pyrotechniccircuit breaker 20 in accordance with the present invention may includean upper housing 22 and a lower housing 30, which may be made of metal,ceramic, or polymer, preferably a suitable high-strength,high-temperature polymer thermoplastic or thermoset such as Ryton®,Amodel®, Ultem®, Phenolic®, Zytel® and the like. The housing maypreferably be constructed as an integral, one-piece, injectionmolded-in-place housing, preferably created by joining together two ormore components. Optionally, a polymer overmolding (preferably selectedfor beneficial cost, formability, and electrical insulationcharacteristics) or a superstructure or skeleton of metal may beutilized for added strength. A pyrotechnic igniter assembly 32 is heldsecurely within the upper housing 22, and the portion of the electricalcircuit to be broken by the output of the pyrotechnic igniter assembly32 is situated between the upper housing 22 and the lower housing 30 andmay preferably take the form of a bolt-on fuse strip 24 (which includesbolt holes 26 for securing the device to a terminal or the like) (or 24′in FIG. 3). The pyrotechnic igniter assembly 32 may preferably be anysuitable reliable, low-cost pyrotechnic device such as an automotiveairbag initiator. The pyrotechnic igniter assembly 32 is thus initiatedby the issuance of an appropriate electrical signal through itsconnector leads, which, for example in the case of an automobile, arepreferably connected to the electronic control unit of the automobile'soccupant restraint system, either as an integral part of the device orat the end of a two-wire cable assembly.

As can be seen, the pyrotechnic igniter assembly 32 is oriented so thatits output is directed through a passage to the bolt-on fuse strip 24,generally perpendicularly to the axis of the bolt-on fuse strip 24.Vents (not shown) through either or both halves of the housing may alsooptionally be provided to safely release the hot gases created byignition of the pyrotechnic igniter assembly 32. Increasing the diameterof the passage between the pyrotechnic igniter assembiy 32 and thebolt-on fuse strip 24 tends to increase the required output of thepyrotechnic igniter assembly 32 and thus may necessitate a strongerhousing (both of which tend to increase manufacturing cost); however,the passage's diameter cannot be decreased arbitrarily as that mayundesirably reduce the ability of the housing to withstand the flow ofhigh or excessive current through the bolt-on fuse strip 24. The heattolerance of the housing may be improved so as to permit furtherreduction of the diameter of the passage, however, such as by formingthe housing of a thermoset type polymer, or by adding heat stabilizersor anti-aging additives to a suitable thermoplastic, or by using a castmetal such as zinc or aluminum (although in that case, electricalinsulation must be provided between the housing and the fuse).

Optionally (as depicted), a projectile 34 may be provided between thepyrotechnic igniter assembly 32 and the bolt-on fuse strip 24 or othersuch portion of the electrical circuit that is to be broken, and if so,the projectile 34 can preferably be integrally molded into the upperhousing 22 as is shown. Upon ignition of the pyrotechnic igniterassembly 32, the projectile 34 breaks free and is propelled into thebolt-on fuse strip 24, with its pointed front portion facilitatingcutting of the bolt-on fuse strip 24. It is noted that the projectile 34does not necessarily need a point or sharp edge, because the action mayprimarily be that of shearing the 24 fuse strip. Also, the projectile 34can made be of the same material as the housing, even if it is polymer,because the action may primarily be a function of the velocity of theprojectile 34 rather than its strength. Thus, the projectile 34 may bemonolithically molded as part of the housing, eliminating a separatepart and the associated cost and scrap, and increasing reliability. Inthat case, the material connecting the projectile 34 to the rest of thehousing preferably may have a cross-section and material strengthselected so as to break upon output with enough energy to accelerate theprojectile 34 to the velocity required to break the fuse strip 24, andis preferably configured so that an edge is formed upon separation ofthe projectile 34 from the housing that may provide a seal to theprojectile 34 as it travels through the fuse strip 24. When theprojectile 34 (which is non-conductive) breaks the fuse strip 24, itpushes the fuse strip 24 into the rupture area 28 (see FIG. 2),preferably locking the broken fuse strip 24 section in place so that itcannot inadvertently re-make the circuit.

Referring to FIG. 2 in particular, it can be seen that a rupture area28, which is an empty cavity, is provided below the bolt-on fuse strip24 between the standoff in the sides of the lower housing 30. As noted,the rupture area 28 accommodates the resulting projection of theadjacent portion of the bolt-on fuse strip 24 when impacted by theoutput of the pyrotechnic igniter assembly 32 or the optional projectile34. The rupture area 28 can also help reduce the heat conducted into theupper housing 22 and lower housing 30 when the bolt-on fuse strip 24experiences an excessive current load.

Referring to FIG. 3 in particular, this embodiment reduces ignitioncharge size for a given sized fuse by focusing ignition gases around thefuse portion to be severed. This increases the local temperature andsevers the fuse by applying drag forces across the thickness of the fusegenerated by high-speed ignition gases and focused force of the ignitionexhaust. The housing is preferably designed to follow the contours ofthe fuse such that the ignition gases can only pass through a narrowaperture (clearance) around the fuse exerting pressure to break it. Thebolt-on fuse strip 24′ has a thickness and minimum fuse width thatcorrespond to the rated amperage of the particular fuse, as is known inthe art. Bolt-on fuse strips are well-known for use in breaking acircuit under high current override conditions. The output of thepyrotechnic igniter assembly 32, and the configuration of the upperhousing 22, lower housing 30, projectile 34 (if any) and rupture area28, should be designed to accommodate the thickness of whatever fuse maybe chosen for use in the circuit breaker, and to ensure reliablebreaking of the fuse upon activation of the pyrotechnic igniter assembly32. Where projectile 34 is not used, the clearance between the peripheryof the fuse strip and the adjacent perimeter of the rupture area has asignificant effect on the rupturing impact of the pyrotechnic output onthe fuse (with less clearance increasing the rupture force exerted).(Although the depicted preferred embodiments utilize a fuse as theportion of a circuit that is formed to be readily broken, which ispreferable, it does not necessarily have to be a fuse).

As shown in FIG. 4, an alternate bolt-on fuse strip 24″ can be providedwith an enlarged impact area 38 that reduces the amount of energy thatmust be produced by the pyrotechnic igniter assembly 32 in order toablate or otherwise break the bolt-on fuse strip 24″, thus permitting(depending on the embodiment) the use of a lower cost pyrotechnicigniter assembly than the one depicted in FIG. 3. This acts like a“force accumulator” and absorbs force generated from the ignitionexhaust, allowing for a smaller ignition charge to sever a given sizedfuse. Alternately, if the optional projectile 34 is omitted, theenlarged impact area 38 can be employed to receive more of the outputenergy of the pyrotechnic igniter assembly 32 so that a larger igniteris not needed.

It has been determined that the embodiment of the invention describedhere can be configured to result in breakage of the circuit in about 0.1to 5 ms, e.g., lms, after issuance of a signal to pyrotechnic igniterassembly 32. Such a fast response time can help reduce the potential forbuildup of heat in wiring and circuitry such as in a vehicle that hasexperienced a collision, prevent electrocutions, and stop fast-movingmachinery or cutting apparatus or other abnormal condition such as inindustrial safety systems.

Turning to FIGS. 5-10, another embodiment of a pyrotechnic circuitbreaker according to the present invention is shown that utilizes a slugto tear a portion of the circuit.

This embodiment of circuit breaker 120 includes an upper housing 122containing an insert-molded pyrotechnic igniter 132 and a lower housing130 containing an empty rupture area 128. Between the upper and lowerhousing is a bolt-on fuse strip 124 with bolt holes 126 at which thecircuit breaker 120 may be attached to the circuit to be protected(e.g., at cables from a power device such as a car battery), such aswith nuts and bolts, preferably mounting the circuit breaker 120 inclose proximity to either the power supply or the circuit to beprotected. The upper and lower housing may be made from the same ordifferent materials, preferably a durable thermoplastic such as Ticona'sPA66 (60% glass filled nylon) with an impact modifier at 10%-20%,preferably 10%-15%, by weight of base material. A suitable impactmodifier mix is 10%-20% Pellathane 2012-65D polyurethane. The upperhousing may be formed of a somewhat lower performance material such asglass-filled nylon, Zytel, or Valox.

Just below the output end of the igniter 132 is a generally cylindricalpassage extending to the top of the strip 124, with a slug 134 locatedin the passage directly between the output end of the igniter 132 and animpact area 138 of the strip 124. The slug 134 is made out of anelectrically non-conductive material and shaped like a puck, preferablyof a diameter about the same as the igniter 132 and just slightly lessthan the passage within which it is located. The slug 134 is eithermolded in place as part of the upper housing 122, or alternately it canbe installed separately. The slug 134 may also serve to partly insulatethe igniter 132 from the high operating temperatures of the fuse.

Adjacent to its impact area 138, the strip 124 includes a necked area139 that tears upon actuation of the igniter 132. As can be seen inFIGS. 7 and 8, the necked area 139 is directly above a laterallyinclined ramp 145 at the top of a base 148 that extends into theotherwise empty rupture area 128. The ramp 145 extends laterallyapproximately the same distance as the narrowed width of the necked area139 of the strip 124, and is preferably molded with a sharpninety-degree angle edge along its length at the front face of the base148. At the bottom of the rupture area 128, the lower housing 130 mayinclude through-holes for venting. More preferably, it may include blindvents 147 closed by a thin layer designed to burst under exhaustpressure, so that the circuit breaker 120 is sealed from the environmentduring normal operation yet able to vent adequately after firing.

To assemble the circuit breaker 120, the strip 124 is snapped into placein the lower housing 130 as shown in FIG. 8, with bosses 146 (which maybe non-uniform to ensure correct orientation of the strip 124) insertinginto corresponding notches defined in the strip 124. The upper housing122 is then slid into the lower housing 130 along the top surface of thestrip 124, with slots 140 in the lower housing 130 and correspondingprotrusions of the upper housing 122 sliding together until the stop 143is reached. Upwardly bent tabs 141 on the strip 124 inhibit the upperhousing 122 from sliding back out, and the upper and lower housing mayalso be provided with mating snap-lock features.

In use, preferably an external, independent source (e.g., sensors, acomputer, and/or a person) determines a condition that warrantsdiscontinuing current flow through the circuit to be protected, andactuates the pyrotechnic igniter 132. The output end of the igniter 132then discharges directly into the slug 134, forcing it into the impactarea 138 of strip 124, and pushing the strip 124 toward rupture area 128and ramp 145 of the lower housing 130. Since the slug 134 substantiallyfills the passage, the slug must completely escape the passage (and thusthe strip 124 must be broken as described below) before exhaust gas fromthe igniter 132 can be released into rupture area 128 and then vented.Consequently, substantially all output energy from the igniter isdirected onto the strip 124, maximizing the force applied to tearing thestrip 124 as described below.

While the slug 134 causes the impact area of the strip 124 to movefreely down into the rupture area 128 without any direct obstructionbelow, the necked area 139 of the strip 124 strikes the aforementionedsharp ninety degree angle edge of the ramp 145 at the front face of thebase 148. The sharp edge acts somewhat like a guillotine, causing thestrip 124 to tear at its necked area 139, progressively along itslateral extent from its side directly above the higher end of the ramp145, to the other side directly above the lower end of the ramp 145. Theangle of incline of the ramp 145 is preferably optimized (according toprinciples well known in the metal stamping art) for the particularconfiguration and materials so that the sharp edge most efficientlytears the strip 124 progressively from end to end rather thanessentially shearing the whole width at once. Since the output energydirected to tearing the strip 124 is maximized as noted above, neither ametal cutting edge for the ramp nor a metal slug is needed, whichreduces possible short circuits after the circuit is broken. After thenecked area 139 of the strip 124 is torn, the non-conductive slug 134 issecurely driven between the broken sides of the necked area 139 of thestrip 124, with blown-out cruciform petals on the output end of theigniter 132 preventing the slug 134 from moving back toward its originallocation, eliminating possible re-connections due to spring-back,jarring of the circuit breaker 120, etc.

Testing of a circuit breaker according to the embodiment of FIGS. 5-10with no metal parts other than the igniter and fuse strip and using onlya 35 mg ZPP charge showed it to reliably break copper fuse strip thick,over a temperature range of −40C to +125C. Such a decreased charge sizeresults in less exhuast gases, and reduces the size and cost of theassembly needed to adequately absorb pyrotechnic shock and containexhuast gases, thus also expanding the range of potential applicationsfor such a circuit breaker.

If desired, electronic circuitry (not shown) may also be incorporatedinto the pyrotechnic circuit breaker 20 or 120, for example inapplications where actuation of the igniter may require a secure digitalsignal for security or safety reasons, e.g., in the case of actuation bylaw enforcement or military personnel in the event of theft, pursuit, etcetera. If included, such circuitry could also be configured to monitor(based on, e.g., inductive field, temperature, or other desired means)the condition of the fuse itself to determine if a condition is presentthat warrants breaking the circuit. In such case, if suitablecurrent-sensing means are employed, the portion of the circuit broken bythe pyrotechnic igniter assembly need not be a fuse but instead cansimply be an ordinary low resistance portion that is formed (e.g., byflattening, widening, necking, and/or scoring) to be readily ablated,torn, or cut.

Although the foregoing description has described the action of thepyrotechnic igniter assembly as sufficient to fully ablate, tear, or cutthe bolt-on fuse strip, other embodiments can readily be conceived inwhich the combination of heat, shock loading, and output gas pressurefrom the igniter breaks, weakens, or damages the fuse so as to decreasethe amount of current required to sever the fuse (or cause it to breakmore rapidly at its rated current). It is also possible that thepyrotechnic igniter assembly can be used as the main actuator of thefuse in response to a command signal as well as in response to anexcessive current load, such as by choosing a configuration andcomposition of the pyrotechnic igniter assembly whereby the igniterauto-ignites in response to heat generated by the fuse during excessivecurrent load.

As will be readily apparent to one in the art, there are a number ofapplications in which suitable embodiments of a pyrotechnic circuitbreaker according to the present invention may be employed. Consideringjust automotive applications by way of example, suitable embodiments maybe used in an automobile to rapidly cut power in the case of a collisionand thus reduce the risk of electrical fire or damage to electricalcomponents. Circuitry generally similar to that used in safety systemcontrollers could also be incorporated to monitor one or more conditionsand when appropriate provide a command to the initiator to break thecircuit, for example, a predetermined amount of time after the initialsensing of a collision. As another example, suitable embodiments of thepresent invention may be employed to disable an automobile (such as inresponse to a command transmitted by the owner, security service vendor,or government personnel) in the case of theft or unlawful operation ofthe vehicle. In such case, other measures known in the art may also beemployed in conjunction so as to reduce the likelihood of immediate lossof control of the vehicle in response to such a command, et cetera.Another application is industrial equipment and personnel safetysystems, such as safety curtains, emergency brakes for fast-movingrotary or linear machinery, cutting blades/apparatus, electrocutionprevention, quick disconnects, etc.

Thus, although the present invention has been described in the contextof one particular preferred embodiment, one skilled in the art willappreciate that numerous variations, modifications, and otherapplications are also within the scope of the present invention. Forexample, the present invention can be used in any suitable applicationin which there is a need for remote or automatic cutting of power in arapid manner, such as in military or commercial vessels or aircraft(e.g., in case of enemy attack), commercial building power controlpanels and oil pipeline pumping stations (e.g., in an emergency such asan earthquake or terrorist attack), munitions or explosive devices(e.g., to disarm associated electronic circuitry), industrial safetycurtains and high speed equipment (e.g., as a rapid power disconnect),and a number of other applications. Thus, the foregoing detaileddescription of preferred embodiments is not intended to in any way limitthe invention, which is limited only by the following claims and theirlegal equivalents.

1. A pyrotechnic circuit breaker for use in an electrical circuitcomprising: a) an electrically conductive portion including means forsecure incorporation into the electrical circuit, and including acurrent load-based fuse; b) a pyrotechnic igniter including an outputend, said pyrotechnic igniter secured so that said output end isoriented toward said electrically conductive portion; c) a passagebetween said electrically conductive portion and said output end of saidpyrotechnic igniter; and, d) a rupture area adjacent said electricallyconductive portion and on the side of said electrically conductiveportion opposite said output end of said pyrotechnic igniter.
 2. Thecircuit breaker of claim 1, wherein said electrically conductive portionincludes a portion that is formed to be readily cut, torn, or ablated.3. The circuit breaker of claim 1, further comprising an electricallynon-conductive housing, wherein said rupture area is defined in saidhousing.
 4. The circuit breaker of claim 1, wherein said electricallyconductive portion is a bolt-on fuse strip.
 5. The circuit breaker ofclaim 1, wherein said electrically conductive portion is formed toreceive a direct ablation force from the pyrotechnic igniter.
 6. Thecircuit breaker of claim 2, further including an electricallynon-conductive mass within said passage between said pyrotechnic igniterand said electrically conductive portion.
 7. The circuit breaker ofclaim 6, further including an electrically non-conductive housing formedof polymer, wherein said electrically non-conductive mass is a slug, andsaid slug is molded into said housing.
 8. A pyrotechnic circuit breakerfor use in an electrical circuit comprising: a) an electricallyconductive portion including means for secure incorporation into theelectrical circuit, a current load-based fuse, and a portion that isformed to be readily cut, torn, or ablated; b) a pyrotechnic igniterincluding an output end, said pyrotechnic igniter secured so that saidoutput end is oriented toward said electrically conductive portion; c) apassage between said electrically conductive portion and said output endof said pyrotechnic igniter; d) a rupture area adjacent saidelectrically conductive portion and on the side of said electricallyconductive portion opposite said output end of said pyrotechnic igniter;and, e) an electrically non-conductive mass within said passage betweensaid pyrotechnic igniter and said electrically conductive portion;wherein said circuit breaker is configured so that after actuation ofsaid pyrotechnic igniter and breaking of the circuit, said electricallynon-conductive mass is securely displaced into a position that preventssaid electrically conductive portion from inadvertently re-closing. 9.The circuit breaker of claim 8, wherein said pyrotechnic igniterincludes cruciform petals on its output end, and wherein saidelectrically non-conductive mass is securely displaced by said cruciformpetals after actuation of said pyrotechnic igniter and breaking of thecircuit.
 10. A pyrotechnic circuit breaker for use in an electricalcircuit comprising: a) an electrically conductive portion includingmeans for secure incorporation into the electrical circuit, andincluding a current load-based fuse; b) a pyrotechnic igniter includingan output end, said pyrotechnic igniter secured so that said output endis oriented toward said electrically conductive portion; c) a passagebetween said electrically conductive portion and said output end of saidpyrotechnic igniter; and, d) a rupture area adjacent said electricallyconductive portion and on the side of said electrically conductiveportion opposite said output end of said pyrotechnic igniter; whereinsaid circuit breaker is configured so that, upon actuation of saidpyrotechnic igniter, substantially all of the output energy of saidpyrotechnic igniter is directed onto said electrically conductiveportion.
 11. The circuit breaker of claim 10, wherein said circuitbreaker includes an electrically non-conductive mass within said passagebetween said pyrotechnic igniter and said electrically conductiveportion.
 12. The circuit breaker of claim 11, wherein said electricallyconductive portion includes a portion that is formed to be readily cut,torn, or ablated.
 13. The circuit breaker of claim 12, wherein saidcircuit breaker and electrically conductive portion are configured sothat upon actuation of said pyrotechnic igniter, said electricallynon-conductive mass causes said electrically conductive portion topredictably progressively laterally tear.
 14. A pyrotechnic circuitbreaker for use in an electrical circuit comprising: a) an electricallyconductive portion including means for secure incorporation into theelectrical circuit, wherein said electrically conductive portion isformed to be readily torn; b) a pyrotechnic igniter including an outputend, said pyrotechnic igniter secured so that said output end isoriented toward said electrically conductive portion; c) a passagebetween said electrically conductive portion and said output end of saidpyrotechnic igniter; and, d) a rupture area adjacent said electricallyconductive portion and on the side of said electrically conductiveportion opposite said output end of said pyrotechnic igniter; whereinsaid circuit breaker is configured so that upon actuation of saidpyrotechnic igniter, said electrically conductive portion predictablyprogressively laterally tears.
 15. The circuit breaker of claim 14,further including a housing having a laterally ramped portionimmediately below said electrically conductive portion.
 16. Apyrotechnic circuit breaker for use in an electrical circuit comprising:a) an electrically conductive portion including means for secureincorporation into the electrical circuit, wherein said electricallyconductive portion is formed to be readily torn; b) a pyrotechnicigniter including an output end, said pyrotechnic igniter secured sothat said output end is oriented toward said electrically conductiveportion; c) a passage between said electrically conductive portion andsaid output end of said pyrotechnic igniter; and, d) a rupture areaadjacent said electrically conductive portion and on the side of saidelectrically conductive portion opposite said output end of saidpyrotechnic igniter; wherein said circuit breaker is configured so that,upon actuation of said pyrotechnic igniter, substantially all of theoutput energy of said pyrotechnic igniter is directed onto saidelectrically conductive portion.
 17. The circuit breaker of claim 16,wherein said circuit breaker includes an electrically non-conductivemass within said passage between said pyrotechnic igniter and saidelectrically conductive portion.
 18. A pyrotechnic circuit breaker foruse in an electrical circuit comprising: a) an electrically conductiveportion including means for secure incorporation into the electricalcircuit, wherein said electrically conductive portion is formed to bereadily torn; b) a pyrotechnic igniter including an output end, saidpyrotechnic igniter secured so that said output end is oriented towardsaid electrically conductive portion; c) a passage between saidelectrically conductive portion and said output end of said pyrotechnicigniter; and, d) a rupture area adjacent said electrically conductiveportion and on the side of said electrically conductive portion oppositesaid output end of said pyrotechnic igniter; wherein said circuitbreaker includes an electrically non-conductive mass within said passagebetween said pyrotechnic igniter and said electrically conductiveportion, and wherein said circuit breaker is configured so that afteractuation of said pyrotechnic igniter and breaking of the circuit, saidelectrically non-conductive mass is securely displaced into a positionthat prevents said electrically conductive portion from inadvertentlyre-closing.
 19. A pyrotechnic circuit breaker for use in an electricalcircuit comprising: a) an electrically conductive portion includingmeans for secure incorporation into the electrical circuit, wherein saidelectrically conductive portion is formed to be readily torn andincludes a current load-based fuse; b) a pyrotechnic igniter includingan output end, said pyrotechnic igniter secured so that said output endis oriented toward said electrically conductive portion; c) a passagebetween said electrically conductive portion and said output end of saidpyrotechnic igniter; and, d) a rupture area adjacent said electricallyconductive portion and on the side of said electrically conductiveportion opposite said output end of said pyrotechnic igniter; whereinsaid circuit breaker is configured so that upon actuation of saidpyrotechnic igniter, said electrically conductive portion predictablyprogressively laterally tears.